(DESCRIPTION (taken directly from the application) Current immunosuppressants used in organ transplantation are administered systematically and have significant toxic side effects. Localized delivery of immunomodulatory molecules to the site of transplanted tissue could theoretically reduce the harmful effects of these gents and could also reduce the vulnerability of patients to infect that comes from systemic immunosuppression. It is possible to manipulate grafts genetically, particularly cellular grafts such as islets, ex vivo, prior to transplantation. Several gene-transfer methods exist for introducing foreign genes into somatic cells, but the efficiency of gene transfer varies greatly among cell types. Since islet cells exist in cluster and do not replicate, it is difficult to transfer genes into islets. Biolistic particle acceleration has been shown to produce efficient transfection of murine islets while preserving function both in vitro and in vivo. We have successfully introduced a reporter gene, green fluorescent protein (GFP), into fresh human and canine islets. We would like to apply this technique to the bioengineering of human islets to express immunomodulatory molecules to produce local immunosuppression. Cellular rejection is a result of an efficient and sustained T cell response. For T cells to be activated fully, binding of antigen/peptide to the T cell receptor and delivery of co-stimulatory signals, usually from a professional antigen presenting cell, must both occur. These co- stimulatory signals may be provided by soluble factors as well as cell surface molecules that bind co-stimulatory receptors on T cells. Inhibitors of co-stimulatory pathways and produce varying degrees of immunosuppression. In addition, current mainstays of clinical immunosuppression such as corticosteroids, cyclosporine, and tacrolimus have all been shown to be toxic to islets and inhibitory to islet function. Recently developed modulators of co-stimulations such as CTLA4Ig and anti-B7 and anti-CD40 monoclonal antibodies do not appear to have the same toxicity for islets. Therefore, we propose to use biolistic particle acceleration to introduce into human islets ex vivo the genetic information encoding modulators of co-stimulatory pathways as a means of inducing local immunosuppression following transplantation. If successful, these studies may provide an alternative to systemic immunosuppression and to gents which are harmful to islet grafts as well as unrelated tissues. The low intrinsic immunogenicity of the biolistic particle carrier and its current clinical uses (ranging from genetic immunization technology to wound healing) suggests this technique could be rapidly and safely introduced into the clinical transplant area.